Tomographic imaging of fracture-fault permeability zones during drilling operations

Abstract

Disclosed are various embodiments of methods for identifying faults and fractures, and other permeable features, within geologic layers during a drilling operation comprising; recording microseismic data during a drilling operation; recording times and positions of a drill bit in a well bore during the drilling operation; processing microseismic data at a plurality of selected times and locations to image microseismic events and identifying faults and fractures, and other permeable features, from corresponding images of microseismic events. In other embodiments, the integrity of a cementing operation may be verified by recording microseismic data during a cementing operation; recording times and positions of a cementing operation in a well bore during the cementing operation; processing microseismic data at a plurality of selected times and locations to image microseismic events and identifying faults and fractures, and other permeable features, within the cemented zone from corresponding images of microseismic events.

We claim:  
     
       1. A method of identifying permeable features proximate a well bore during a drilling operation, comprising:
 recording, over first periods of time, a microseismic data set during the drilling operation; 
 recording, over second periods of time, drill bit positions, and times corresponding to the drill bit positions in the well bore during the drilling operation to form a drill bit position and time data set; 
 correlating times of recording the microseismic data set with the drill bit positions and times corresponding to the drill bit positions recorded in the drill bit position and time data set; 
 processing the microseismic data set at a plurality of selected times to generate microseismic event images associated with or arising from the drilling operation at drill bit positions in the well bore corresponding to said selected times, and 
 identifying said permeable features proximate the well bore from the microseismic event images. 
 
     
     
       2. The method of  claim 1 , wherein drill bit positions and corresponding times are substantially continuously recorded. 
     
     
       3. The method of  claim 1 , wherein recording microseismic data during a drilling operation further comprises continuing to record microseismic data after cessation of drilling until microseismic activity resulting from the drilling operation has substantially ceased. 
     
     
       4. The method of  claim 1 , wherein the microseismic data are processed with SET software. 
     
     
       5. The method of  claim 1 , wherein the microseismic data are processed using an estimated velocity model derived using SET processing of the microseismic data to image a plurality of positions of the drill bit corresponding to known times and positions of the drill bit. 
     
     
       6. The method of  claim 1 , wherein the microseismic data are processed using an estimated velocity model derived from analysis of conventional surface seismic data. 
     
     
       7. The method of  claim 1 , wherein the microseismic data are processed using an estimated velocity model derived from analysis of well log data. 
     
     
       8. The method of  claim 1  wherein the plurality of selected times is determined by selecting a predetermined time increment during the drilling process. 
     
     
       9. The method of  claim 1  wherein the plurality of selected times is determined by selecting times corresponding to a predetermined depth increment during the drilling process. 
     
     
       10. The method of  claim 1  wherein the plurality of selected times is determined by selecting times corresponding to a predetermined set of time or depth values during the drilling process. 
     
     
       11. The method of  claim 1  wherein the plurality of selected times is determined by selecting times corresponding to events observed during the drilling process. 
     
     
       12. The method of  claim 11  wherein the events observed during the drilling process further comprise a drop in the pressure of the drilling fluid. 
     
     
       13. The method of  claim 11  wherein the events observed during the drilling process further comprise a loss of drilling fluid. 
     
     
       14. The method of  claim 11  wherein the events observed during the drilling process further comprise a change in the rate of drilling corresponding to a change in properties of a geologic layer. 
     
     
       15. The method of  claim 1  further comprising determining zones of high permeability by identifying faults and fractures from said microseismic event images. 
     
     
       16. The method of  claim 1  further comprising determining zones of low permeability by identifying faults and fractures or the lack thereof from said microseismic event images. 
     
     
       17. The method of  claim 1  further comprising determining zones suitable for hydraulic fracturing by identifying faults and fractures or the lack thereof from said microseismic event images. 
     
     
       18. The method of  claim 1  further comprising determining zones not suitable for hydraulic fracturing by identifying faults and fractures or the lack thereof from said microseismic event images.